基于Mie理论的四种典型水云的光散射计算

在Mie理论的基础上,利用修正伽马函数来描述水云的粒子尺度分布,计算了一类层云、二类层云、一类层积云和二类层积云这四种典型水云的消光系数、单次散射反照率、不对称因子和散射相函数.结果表明,粒子的消光系数、单次散射反照率和非对称因子随着入射波长的增加有较大的起伏,后两者随着波长的增加其变化趋势基本一致;消光系数主要受云中液态水含量的影响;对于单次散射反照率来说,在可见光波段,反照率非常接近于1;在短波段,粒子的非对称因子变化较小,并且随着波长的增加,非对称因子会逐渐增大;Mie相函数随着散射角的增加呈现出先减小后增大的趋势,但相函数随着波长的增加,并没有呈现出简单的线性关系.

Calculation of light scattering on water cloud particles by using Mie's theory

Based on Mie's theory, the extinction coefficient, the single scattering albedo, the asym-metry factor and the scattering phase function of the four typical water clouds were calculated by using the amended gamma function to describe the particle size distribution. The four typical water clouds include the stratus Ⅰ , stratus Ⅱ, the cumulus layer Ⅰand the cumulus layer Ⅱ clouds. The simulation results show that, the extinction coefficient, single scattering albedo and asymmetry factors change evidently with the incident wavelength;Extinction coefficient is mainly affected by cloud liquid water content;Single scattering albedo and asymmetry factors change identically with the incident wavelength;Within the visible band, the single scattering albedo is close to 1. Within the short wavelength range, the value of the asymmetry factors is small and increases with the inci-dent wavelength, Mie phase function shows a trend of decreasing firstly and then increasing along with the increasing scattering angle. However, phase function doesnt show simple linear relationship with wavelength as the wavelength increases.